Reaction Wheel Assemblies (RWAs) are routinely deployed onboard satellites and other vehicles for attitude adjustment purposes. By common design, an RWA contains a rotor having a rotor shaft, which is fixedly joined to an inertial element (e.g., an outer rim or ring) by a suspension web. The rotor may be mounted within a housing assembly having upper and lower halves, which are sealingly joined to enclose the rotor. The opposing ends of the rotor shaft are received within cylindrical cavities or bores provided in the RWA housing assembly. Spin bearings, such as duplex pair ball bearings, are positioned around the opposing shaft ends to provide a rotor suspension, which generally limits freedom of rotor motion relative to the housing assembly in all directions except for rotation about a spin axis. During RWA operation, a spin motor drives rotation of the rotor about the spin axis at a relatively high rate of speed to create momentum. When it is desired to adjust the attitude of the host vehicle, control circuitry commands the spin motor to alter the rotational speed of the rotor and, therefore, the momentum of the inertial element. Due to this momentum change, a controlled output torque is generated and transferred from the RWA to the host vehicle to effectuate the desired attitude adjustment. Three or more RWAs can be combined with mounting hardware to produce an RWA system capable of performing highly controlled attitude adjustments about orthogonal axes in three dimensional space.
As satellites increase in number and decrease in size, a demand has arisen for increasingly compact, lightweight, relatively low cost, and readily manufacturable RWAs adapted for deployment onboard so-called “small satellites” or, more simply, “smallsats.” Although a universal definition is yet to be established, a satellite weighing less than 400 kilograms is often considered a “small satellite.” Small satellites include, for example, miniaturized cube-shaped research and communication satellites commonly referred to as “cubesats.” As the demand for small scale RWAs has increased, so too has the demand for RWA systems similarly characterized by relatively compact form factors and high mass efficiencies. Such RWA systems are desirably not only highly mass efficient, but are also ideally manufacturable at competitive costs and capable of prolonged, failure free, spaceborne operation comparable to that traditionally provided by legacy RWA systems. Embodiments of RWA systems having such desirable attributes are disclosed herein. Additionally, in certain embodiments, the below-described RWA systems feature highly modular designs, which allow enhanced flexibility in satellite mounting solutions and streamlined RWA maintenance.